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For my final project I built a sous-vide immersion cooker

fab.cba.mit.edu

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Re: For my final project I built a sous-vide immersion cooker

#71

Post by jwr »

abakker wrote: post #60
arbesfeld wrote: post #57

Earlier quoted context omitted.

Great points, I do think that a professional PID is a better and more efficient way to build a sous-vide. I wanted to build something from basic components instead as part of the learning process, and also to allow me customize the logic via Bluetooth. Regarding the steak, I find that a 1 inch thick steak only takes ~45 minutes to reach the target internal temperature. This scales dramatically as the steak thickness…

because the temperatures inside are below instant pasteurization temperatures (158°F) though, reaching the target is insufficient. They need to be held at the target temperature over a period of time to guarantee sufficient pasteurization. I'll also agree that the learning process can't be beat the way you did it. I suppose you could simulate the PID function in software on the arduino though - http://playground.ardu…

Be careful with Arduino libraries. If you are trying to learn something, it's usually better to write your own, or look at really good code.

Case in point, PIDLibrary, I'm looking at the PIDCompute function, line 57:

      ITerm+= (ki * error);
That's not how you deal with I. You are supposed to accumulate (integrate) the error and multiply by Ki only for the final PID addition. You don't want to accumulate your errors multiplied each time by Ki, it makes no sense.

Re: For my final project I built a sous-vide immersion cooker

#72

Post by djrogers »

abakker wrote: post #60
arbesfeld wrote: post #57

Earlier quoted context omitted.

Great points, I do think that a professional PID is a better and more efficient way to build a sous-vide. I wanted to build something from basic components instead as part of the learning process, and also to allow me customize the logic via Bluetooth. Regarding the steak, I find that a 1 inch thick steak only takes ~45 minutes to reach the target internal temperature. This scales dramatically as the steak thickness…

because the temperatures inside are below instant pasteurization temperatures (158°F) though, reaching the target is insufficient. They need to be held at the target temperature over a period of time to guarantee sufficient pasteurization. I'll also agree that the learning process can't be beat the way you did it. I suppose you could simulate the PID function in software on the arduino though - http://playground.ardu…

Steak is generally safe to consume at any temperature as long as the exterior surface (where any nasties would live) is seared, which takes it well above 158*.

Ever heard of steak tartare? Delicious...

Re: For my final project I built a sous-vide immersion cooker

#73

Post by _pius »

blhack wrote: post #66
tptacek wrote: post #58

Earlier quoted context omitted.

It's a great writeup!

I've seen you comment a lot on sous vide in the past, is there a specific machine that you recommend? (And then is there one you'd recommend if money was no object)

I own the Sansaire, but right now I'd recommend the new Anova one that comes with an app and is well-reviewed by Serious Eats.

http://anovaculinary.com/products/anova-precision-cooker

http://www.seriouseats.com/2014/05/new-anova-precision-cooke...

Re: For my final project I built a sous-vide immersion cooker

#74

Post by vonmoltke »

tzs wrote: post #67

I have a couple of questions about the schematic. R4 and R5 are 0K resistors. 0K resistors actually exist, and are typically used in place of short pieces of wire. The advantage of a 0K resistor over a short piece of wire is that they can be picked and placed and soldered using the same equipment that handles resistors, thus saving the need of having a separate machine for short wires. That is how they are being used…

A 0 ohm resistor typically is only used for places where a different-valued resistor could be substituted or used to exist, or to act as an optional jumper on different revisions of hardware. In those cases, the resistor is in the schematics.

A circuit designed from the start with a 0 ohm resistor that was just used for connecting two points across some board feature would never make it past review where I used to work. Such a situation may come up due to later design changes or board damage, in which case the board is modified by use of a "blue wire", which is an actual blue-insulated wire that makes a point-to-point connection on the surface of the board. Those are not in the schematic.

That said, I used to work on military electronics. Perhaps the consumer electronics world is different.

Re: For my final project I built a sous-vide immersion cooker

#75

Post by mikecb »

_pius wrote: post #73
blhack wrote: post #66

Earlier quoted context omitted.

I've seen you comment a lot on sous vide in the past, is there a specific machine that you recommend? (And then is there one you'd recommend if money was no object)

I own the Sansaire, but right now I'd recommend the new Anova one that comes with an app and is well-reviewed by Serious Eats. http://anovaculinary.com/products/anova-precision-cooker http://www.seriouseats.com/2014/05/new-anova-precision-cooke...

Do you know if they've released the android app yet? You can use it without (has a little wheel to set temp), but the monitoring and timing obviously don't work.

Re: For my final project I built a sous-vide immersion cooker

#76

Post by abakker »

djrogers wrote: post #72
abakker wrote: post #60

Earlier quoted context omitted.

because the temperatures inside are below instant pasteurization temperatures (158°F) though, reaching the target is insufficient. They need to be held at the target temperature over a period of time to guarantee sufficient pasteurization. I'll also agree that the learning process can't be beat the way you did it. I suppose you could simulate the PID function in software on the arduino though - http://playground.ardu…

Steak is generally safe to consume at any temperature as long as the exterior surface (where any nasties would live) is seared, which takes it well above 158*. Ever heard of steak tartare? Delicious...

Yeah - I've had plenty of steak tartar, and it is delicious. The difference here is that with steak tartar, you know you are eating raw meat. With Sous Vide, you assume you'll be eating safe meat. It is doubly important in sous vide to reach pasteurization because of the extended period of time spent in the bacterially friendly temperatures.

Its a good point about the exterior surface, but the blog post also shows him cooking a hamburger.

Re: For my final project I built a sous-vide immersion cooker

#77

Post by [deleted] »

tptacek wrote: post #69
blhack wrote: post #66

Earlier quoted context omitted.

I've seen you comment a lot on sous vide in the past, is there a specific machine that you recommend? (And then is there one you'd recommend if money was no object)

Whichever of Anova, Sansaire, and Polyscience is cheapest at the time.

[deleted]

Re: For my final project I built a sous-vide immersion cooker

#78

Post by cnvogel »

Hey arbesfeld, I really like that project, and the nice writeup really presents it well. But especially as people might use it for inspiration for their own temperature-controlled cooking projects, I think the lack of a proper isolation of the mains-powered parts is a little bit worrying.

For the next project, or maybe as advice to the random person looking at the HN comments, here's what I normally do:

Try to minimize the area of unisolated conductors in devices on which you work. If I solder cables to e.g. a mains inlet, I'd put heat-shrink-tubing over it, so that it's not touchable anymore. Or use the proper crimped terminations, which also are available in isolated versions.

https://www.google.de/search?q=flachstecker&tbm=isch

To protect braided wire, and make the connections more reliable over time, I like to use "wire termination" (I don't know the correct english term, in Germany we call them Aderendhülse (literally: conductor end sheath).

https://www.google.de/search?q=aderendhülse&tbm=isch

Instead of these "screw on caps" for cables, try to find suitable terminal blocks.

If you have the possibility to access a 3D printer, make a small clip that goes over the screw-terminals of the solid-state relay.

If possible, try to have a "high-voltage" and a "low voltage" side in your enclosure, that way, you are even less likely to come in contact with mains voltage while working e.g. on the MCU part (connecting/disconnecting the programming cable).

I'd like to stress again: I really like your project as presented, I only want to show some ways in which the project could serve maybe as a inspiration also to safe mains-powered electronic design.

Re: For my final project I built a sous-vide immersion cooker

#79

Post by arbesfeld »

cnvogel wrote: post #78

Hey arbesfeld, I really like that project, and the nice writeup really presents it well. But especially as people might use it for inspiration for their own temperature-controlled cooking projects, I think the lack of a proper isolation of the mains-powered parts is a little bit worrying. For the next project, or maybe as advice to the random person looking at the HN comments, here's what I normally do: Try to minimi…

Thanks for the tips. This was my first time working with power components and I wasn't familiar with most of these parts. I'll incorporate these suggestions into the blog post so that they can be a resource to others.
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